We already covered how to install Chrome and Firefox add-ons manually,of course we also covered install & uninstall of extensions for opera .Opera extensions can be made of CSS,HTML and JavaScript.Do you know Opera extension file is of OEX format, where as Chrome extension file is CRX and Firefox add-on’s extension is XPI.

This is another way of installing Opera extension which can be helpful when you are unable to install extension directly from Opera extensions site.